Sequential injection molding techniques have been utilized for a number of years. U.S. Pat. No. 5,762,855 describes a method for molding large components in a mold having one mold cavity. Plasticized material is introduced into a single cavity mold through a manifold. The manifold has at least two spaced valve gates that are independently opened and closed as directed by a controller to selectively communicate plasticized material from the manifold to the mold cavity at separate locations in the mold cavity. The controller directs the valve gates to sequentially open and close during the filling phase so as to achieve the desired melt front advancement within the mold cavity. Once the mold cavity has been filled, the valve gates are closed to effectively seal the manifold from the mold cavity. The closed valve gates thereby assist in allowing the plasticized material within the manifold to be held in compression while the mold cavity is open for removal of the molded component from the mold cavity, so as to prevent appreciable expansion of the material that has been found to result in imperfections, such as splay, in molded products.
However, flash, the portion of melted material escaping between the two mold halves that form the mold cavity, continues to be a problem. Sometimes the problem is so severe that the molded component must be discarded. To correct the flash error would be prohibitively expensive with respect to the manual labor needed to remove the flash from each molded component. Also, sometimes the molds are underfilled, resulting in molded components that must be discarded. Many times the molding material may not even be recoverable from the incorrectly molded component. In addition, successively molding individual components is time-consuming. Thus, to be cost-effective, the molding process needs to be more closely controlled to avoid over-filling and underfilling of the mold. Additionally, increasing the number of molded products produced in a single cycle would also improve efficiency.